It is known that cell growth or proliferation is promoted by binding of the epidermal growth factor (hereinafter referred to as “EGF”) as a ligand to an extracellular domain of a receptor on the cell surface, i.e., epidermal growth factor receptor (hereinafter referred to as “EGFR”). Particularly, it has been found that EGFRs are overexpressed on the surface of various tumor cells and are deeply involved in growth and malignant conversion of the tumors.
Therefore, development of drugs which can block the binding of EGF to EGFRs to block signal transduction to which EGFRs are involved, resulting in suppression of growth of malignant tumor cells, particularly antibody drugs (anti-tumor drugs) mainly including antibodies which specifically bind to EGFRs (anti-EGFR antibodies) have been in progress. For example, anti-EGFR antibodies, matuzumab and cetuximab, have been known which can bind to EGFRs competitively with EGF, thereby inhibiting activation and dimerization of EGFRs, and their certain benefits have been shown in growth suppression (growth inhibition) of malignant tumor cells such as colon cancer cells. Patent Literature 1 discloses an example of conventional antibodies of this type and a production example thereof.